Many modern ophthalmic surgical procedures require accurate measurements of the eye. For example, measurements of aberrations of the eye are important for the diagnosis and treatment of visual defects and acuity. Furthermore, there are a growing number of ways that aberrations can be corrected using both surgical and non-surgical means. Many of these methods rely on accurate, precise measurements of the whole ocular system so that patients may be screened, the corrective means applied and tested, and follow-up care provided as appropriate.
One type of ocular measurement is generally referred to as ocular topography. In general, ocular topography is the measurement of the surfaces in an ocular system. For example, ocular topography can include the determination of the surface shapes of the cornea and lens. Each of these measurements can be useful in various surgical and non-surgical treatments, and improved accuracy and precision of these measurements may lead to improved methods for correcting visual defects, and for identifying patients in need of care.
Another type of ocular measurement is generally referred to as aberrometry. In general, aberrometry is the measurement of the effects of aberrations or refractive errors in the eye. Thus, aberrometry can provide a measurement of the optical quality of the eye, including the overall quality and local variations in quality. Typically, aberrometers can measure spherical and cylindrical aberrations. Some aberrometers can additionally measure higher order aberrations. Again, each of these measurements can be useful in various surgical and non-surgical treatments, and improved accuracy and precision of these measurements may lead to improved methods for correcting visual defects, and for identifying patients in need of care.
A variety of newer multifunction devices have become available that can measure both ocular topography and aberrometry. However, these multifunction devices can suffer from a variety of issues. For example, the accuracy of multifunction devices can be impaired without precise alignment between the different imaging devices used for ocular topography and aberrometry. Such precise alignment can usually be accomplished through calibration and the use of measured offsets, but in some cases misalignment may still occur and result in impaired accuracy. Furthermore, the use of two imaging devices can result in imaging at slightly different angles, with the possible result of impaired accuracy.
For these and other reasons there is a continuing need for improved ocular topography and aberrometry devices and techniques.